Wave-signal responder system



Oct. 3, 1950 M. K. TAYLOR 2,524,491

WAVE-SIGNAL RESPONDER sYs'rsu Filed July 12, 1947 INVENTOR. MAURICE K. TAYLOR ATTORNEY Patented Oct. 3, 1950 2,524,491 ICE 2,524,491 WAVE-SIGNAL RESPONDER SYSTEM Maurice K. Taylor, Hollinwood,-England, assignor to Ferranti Limited, Hollinwod, "England, a corporation of Great Britain Application July 12, 1947, Serial No. 760,563 In Great Britain November 5, 1945 Section 1, Public Law 690, August18, 1946 Patent expires November 5, 1965 I i This invention relates to apparatus for use in wireless signaling systems of the kind in which a transmitter having a receiver associated therewith, is arranged to radiate a response signal in reply to an interrogation signal received by such associated receiver.

More particularly the invention relates to such receiver-transmitter devices, usually known as responders, of the type adapted for use with a pulsed interrogating signal and is an improvement in or modification of the responder 'described and claimed in an application of F. C. Williams, Serial No. 692,085, filed August 21, 1946.

In such a responder, hereinafter referred to as a responder of the type stated, the driving potential applied to the transmitting valve to produce a state of powerful oscillation therein, must be high, since under normal operating conditions, the control grid of the transmitting valve takes a relatively large current. The source of such driving potential should therefore have a low impedance. This driving potential is normally derived from the anode load of a pentode amplifier valve whose input is supplied by the rectified received signal output of the associated receiver. In order to obtain a high amplification from such pentode amplifier a high resistance is connected in its anode lead, thereby making its output impedance large; thus the driving potential obtained when a large current is drawn therefrom is not as large as that which would be obtained from a source having a much smaller output impedance.

It has been proposed in a copending application of Maurice K. Taylor et 2.1., Serial No. 762,642, filed July 22, 1947, entitled Wave-Signal Responder System, and assigned to the same assignee as the present application, that in order to avoid this difiiculty there be employed a stage having a valve with a load impedance in its cathode circuit as a low-impedance driving potential source for the transmitting valve.

With such an arrangement it is essential that the pulse fed back to the control grid of the transmitting valve from the cathode load impedance is of the correct phase, that is to say, a positive pulse must be fed from the cathode load impedance to the control grid of the transmitting valve to ensure that the transmitting valve is triggered when an interrogating signal pulse is received. For the purpose of obtaining such a positive pulse, the amplifier valve preceding the cathode loaded valve stage must be arranged so that its control grid is driven negatively by the rectified received pulse signal and must, in consequence, take a large current in the absence of reception and retransmission of a signal pulse by the responder.

5 Claims. (01. 2504'?) 1 is connected by way of resistance S, blocking con- It will be seen that when such a responder is not receiving signal pulses, the power consumption is large.

The main object of the present invention isto provide an improved form of responder of the type stated in which a high driving power is applied to the transmitting valve and in which the power consumption from the high-voltage energizing supply source is considerably reduced.

According to the present invention a wave-signal responder system comprises a wave-signal receiver for receiving an interrogating pulsemodulated wave signal and for deriving the pulsemodulation components thereof to provide a control signal of pulse wave form. The system also includes an amplifier valve for amplifying the control signal, a transmitter including a transmitting valve having 'a cathode and a control electrode normall biased to maintain the transmitting valve at substantially anode-current cutoff, .and a step-down transformer coupled to the output circuit of the amplifier valve and having a winding of low impedance coupled between the oathode and the control electrode of the transmitting valve for applying the amplified output signal of the amplifier valve to the transmitter valve as a controlling, potential to bias the control electrode to such a value of positive potential relative to the cathode upon the occurrence of each pulse of the signal that each such pulse initiates operation of the transmitting valve.

The invention will now be described by way of example with reference to the accompanying drawing which shows the circuit of a responder of the type stated embodying the present invention.

For a better understanding of the present invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanying drawing, and its scope will be pointed out in the appended claims.

This responder includes a superregenerative radio-receiving stage consisting of a triode valve I forming part of a Hartley-type oscillator, the cathode 2 of this valve being connected to the earthed negative pole -B of a high-voltage supply +B byway of biasing resistance 3 and decoupling condenser E. An aerial, not shown, is coupled by coil 5 to inductance 6 shunted by variable condenser 6a and forming a tuned circuit for the oscillator, the mid-point 6' of the inductance being connected to the positive pole +B of the high-voltage supply.

A quench-frequency oscillator is provided consisting of a triode valve 1 connected as a con: ventional ised-back oscillator. The high-potential end oi inductance winding 8 of this oscillator 3 denser In and radio-frequency choke II to the control grid l2 of superregenerative valve I. A

grid-leak resistance I2 is connected between grid 12 and the negative pole of the high-voltage supply.

One end of the tuned circuit 6, 6a is connected by way of condenser it to the control grid 12 of valve l and also by way of condenser 13 to the control grid 14 of a triode transmitting valve 15, the anode 16 of which is joined to the other end of tuned circuit 6 as is the anode [6 of valve l. The cathode l! of valve is returned to earth by way of biasing resistance l8 and decoupling condenser 19. Anode I6 is connected by way of condenser 20 to anode 2| of diode detector valve 22 the cathode 23 of which is connected to earth by way of load resistance 44. Anode 2| is also connected to earth by way of resistance 24. Cathode 23 of this diode valve is joined by way of radio-frequency choke 25 to the control grid 26 of pentode amplifier valve 21, the oathode of which is connected to earth by way of a biasing resistance 23 and a decoupling condenser 29. The anode 36 of valve 21 is joined to the positive pole of the high-voltage supply by way of the primary winding of a step-down transformer 46 and a resistance 3!. One end of the secondary winding 41 of transformer 46 is earthed and the other end is connected by way of a pulsewidening circuit comprising a condenser 39 and a resistance 4| and then by way of a radio-frequency choke 40 to control grid IA of transmitting valve 15. Cathode ll of valve I5 is joined to the positive terminal of the high-voltage supply by way of a resistance 43.

In operation, as a result of the superregenerative reception of a signal pulse by valve I, the potential of cathode '23 of diode valve 22 becomes more positive due to the rectified current flow through the diode load resistance 44. Thus control grid 26 becomes more positive and the resultant rise in the anode current of valve 21 causes, by appropriate sensing of the connections of transformer 46, the application .of a positive signal pulse to control grid Id of transmitting valve 16 by way of pulse-widening condenser 39 and resistance ll. This initiates operation of the valve l5 by altering the bias voltage on the control grid to a value at which oscillation starts.

This oscillation builds up and is radiated from the aerial by way of coil 5. The duration of the radiated response pulse is determined by the time constant of the control grid circuit of valve [5, and more particularly by the values of condenser 39 and resistance 4%, the termination of each response pulse being caused by a grid-squegging action due to the grid-current fiow in valve 15.

The step-down transformer 46 provides a lowimpedance source of driving power and since a positive potential is applied to control .grid 26 on reception of a signal pulse, amplifier valve 21 need only take small current when the apparatus is not receiving signal pulses, i. c. it may be biased nearly to cutoff by the resistance 28. Resistance 43 causes current flow through re.- sistance l8 to provide a negative grid bias potential suificient to maintain valve H3 in the cutoff region during periods between retransmission of coded pulses.

Radio-frequency choke 46 reduces or eliminates radio-frequency losses resulting from the connection of transformer winding 41 to control grid I4.

While there has been described what is at present considered to be the preferred embodiment of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. A wave-signal responder system comprising, a wave-signal receiver for receiving an interrogating pulse-modulated wave signal and for deriving the pulse-modulation components thereof to provide a control signal of pulse wave form, an amplifier valve for amplifying said control signal, a transmitter including a transmitting valve having a cathode and a control electrode normally biased to maintain said transmitting valve at substantially anode-current cutoff, and a step-down transformer coupled to the output circuit of said amplifier valve and having a winding of low impedance coupled between said cathode and control electrode of said transmitting valve for applying the amplified output signal of said amplifier valve to said transmitter valve as a controlling potential to bias said control electrode to such a value of positive potential relative to said cathode upon the occurrence of each pulse of said signal that each said pulse initiates operation of said transmitting valve.

2. A wave-signal responder system comprising, a wave-signal receiver for receiving and rectifying interrogating pulse-modulated wave signals and for applying the recrified signals as a positive direct-current potential to an amplifier valve for amplification of said rectified signals, means including a transmitting valve controlled by said amplified signals to transmit wave signals of modified pulse wave form, said transmitting valve having a cathode and a control electrode and a step-down transformer coupled to said amplifier valve and having a winding of low impedance coupled between said control electrode and cathode for translating amplified signals from said amplifier valve to said transmitting valve to effect said controlled operation thereof by driving said control electrode to a positive potential relative to said cathode upon the occurrence of each pulse of said signal.

3. A wave-signal responder system as claimed in claim 1 in which said control signal is applied to a control grid of said amplifier valve as a positive unidirectional potential.

4. A wave-signal responder system as claimed in claim 1 in which said transformer is coupled to said transmitting valve through means for modifying the width of the pulses of said amplified control signal.

5. A wave-signal responder system as claimed in claim 4 in which said Width modifying means comprises a parallel connected resistance-capacitance network.

MAURICE K. TAYLOR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

